Maxperson
Morkus from Orkus
A normal fighter also spends his action and reaction, and for a single weapon attack that can miss. The only difference between that fighter and the one using the magic action to fireball or wall of fire someone is concentration. I don't think taking up concentration for 1 round is anywhere near a big enough sacrifice to account for the difference between a single weapon attack that can miss and a spell that can deal a lot of damage and/or control the battlefield.OR, hear me out:
3) they thought that having to spend your action and reaction and your concentration, and still have a chance that the trigger never comes up or you lose concentration, was sufficient additional drawbacks and costs that casting a spell this way was reasonable and didn’t need to be prevented.
Plus, as was mentioned, it's super easy to pick a trigger that is going to happen. Readied actions are rarely wasted.